Simulation of plastic flow driven by periodically alternating pressure and related deformation mechanism in linear friction welding

Abstract

Comprehensive understandings of plastic flow and microstructure development are vital to control the product performance in friction-based solid-state welding. Presented in this paper is a three-dimensional fully coupled mathematical modeling for plastic flow driven by periodically alternating pressure in linear friction welding. A plastic/plastic friction pair model is proposed to describe the friction interface condition, where the modified Coulomb model is used to calculate the frictional heat. Numerical simulations are well validated by experiments. Results show a significant periodicity in the variation of plastic flow and deformation fields. Two workpieces alignment leads to a periodic extrusion and backflow of materials, which results in a fluctuating increase in the burn-off length. As process reaches the quasi-steady-state stage, compressive deformation plays a predominant role near the interface while shear deformation periodically occurs near the periphery of the interface only as the oscillatory velocity becomes zero. By consideration of plastic flow deformation, the weld microstructure of joint is investigated experimentally. Plastic deformation behavior exhibits high sensitive to welding parameters. Material flow velocity at the interface increases at greater oscillatory parameters owing to higher interfacial temperature, but decreases with increasing friction pressure due to the reduction of interfacial temperature and increment of strain rate.